Smithsonian miscellaneous collections . ular when not covered bythe detritus at the foot. The face of the ice was also irregularlymelted, due to the more exposed position of some part<. Maddren : Loe. cit, p. 18. EXPLORATION IN ALASKA IN IOX)/ GILMORE 21 Upon ascending to the top of the escarpment at the point mostremote from the river, it was found that a mass of frozen muck,estimated to be two hundred feet long and fifteen to twenty feet inthickness, with a vertical face of twenty to thirty feet, had movedoutward at its, center for fully fifty feet, but had not yet becomedetached at its e
Smithsonian miscellaneous collections . ular when not covered bythe detritus at the foot. The face of the ice was also irregularlymelted, due to the more exposed position of some part<. Maddren : Loe. cit, p. 18. EXPLORATION IN ALASKA IN IOX)/ GILMORE 21 Upon ascending to the top of the escarpment at the point mostremote from the river, it was found that a mass of frozen muck,estimated to be two hundred feet long and fifteen to twenty feet inthickness, with a vertical face of twenty to thirty feet, had movedoutward at its, center for fully fifty feet, but had not yet becomedetached at its ends. The crevasse formed by this displacement wasfilled by water to such a depth that the bottom could not be foundwith a long pole. Back of the crevasse, in the surface of the numerous parallel cracks varying from six to eighteen inchesin width and many feet in length. These had water standing inthem nearly to the top of the ground. The conditions observedhere appeared to the writer to explain the presence of the ice on the. Fig. 3.—Cross-section of Palisades Escarpment, showing Formation of Superficial Ice. 1-2-3. Blocks of frozen silt; 4-5. Water level of the Yukon; 4-6. 150-170feet; 7. Crevasse filled with water; 8. Ice on faces; 9. Overhanging turf;10. Lacustrian silts; n. Detritus (thawed muck). faces below. With the advent of winter, assisted by the alreadyfrozen ground, the water in the crevasses becomes frozen solid. Asubsequent outward movement of the blocks would leave the iceclinging to the face of either the cliff, or the block, or both, andunder the influence of the rays of the summer sun would rapidlysmooth the broken and ragged edges. On the faces of blocks I and2 (see fig. 3) such layers of ice were observed, and where protectedby the wet mantle of overhanging turf and moss were thawing veryslowly. In places the ice was so thin the writer with a few strokesof his pick was able to penetrate it and into the frozen muck wallbehind. Sections of the ice
Size: 2241px × 1115px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
